Flexible biopsy needle

ABSTRACT

A flexible biopsy needle assembly includes a flexible coring stylet that is slidably disposed within a flexible outer cannula. The stylet includes an elongated body, a tip, a sampling notch adjacent to the tip, and at least one ferrule along the length of the body. The cannula includes an elongated tubular body defining a lumen sized for sliding passage of the stylet, a cutting edge at the opening of the lumen, and an array of slits along the length of its body. The slits are sized to allow the diameter of the ferrule(s) to extend partially therein. The slits and ferrule(s) interact to limit or control the flexibility of the cannula at the location of the slits.

REFERENCE TO RELATED APPLICATION

This application claims priority to co-pending provisional applicationNo. 61/182,248, filed on May 29, 2009, the disclosure which isincorporated herein by reference.

BACKGROUND

The present disclosure relates generally to biopsy systems andspecifically to devices for obtaining biopsy samples through veins andarteries.

In the practice of diagnostic medicine, it is often necessary ordesirable to perform a biopsy, or to sample selected tissue from aliving patient for medical evaluation. Cytological and histologicalstudies of the biopsy sample can then be performed as an aid thediagnosing and treating various forms of cancer, as well as otherdiseases in which a localized area of affected tissue can be identified.

Special considerations apply if the biopsy is to be performed on aninternal organ deep within the body, such as the liver. Previously,obtaining a tissue sample from an internal organ, such as the liver, wascarried out percutaneously by entering the skin in the vicinity of theorgan and thereafter extracting a core of liver material through thebiopsy needle. This method, although effective in obtaining an adequateamount of tissue from the liver, has a risk of serious healthcomplications to the patient caused by the biopsy. For example, patientsgenerally experience extreme pain, and additionally, the liver profuselybleeds after a percutaneous biopsy.

Alternatively, tissue samples may be obtained without the problemsassociated with a percutaneous biopsy by accessing the liver via atransjugular procedure. Known techniques involve accessing the liverthrough the jugular vein with an elongated biopsy device. Typically,these biopsy devices are identical to typical single and double actionbiopsy devices, except that the inner and outer needles are elongated toaccess the liver from the jugular vein.

A problem associated with this type of biopsy device is that the rigidinner and outer needles are commonly metallic and lack the flexibilityto navigate through venous passageways to the targeted tissue site.However, biopsy of an organ deep within the body, such as the liver,requires the biopsy device to be implanted at a significant depth. Sincethe quality of the specimen is largely dependent on the strikingmomentum of the biopsy device over this long distance, a degree ofstiffness of the needles is necessary to transmit striking force fromthe firing device to the tip of the coring needles. Thus, what is neededis a needle assembly that provides flexibility without compromising thestiffness and integrity of the needles.

SUMMARY

A flexible biopsy needle assembly includes a flexible coring stylet thatis slidably disposed within a flexible outer cannula. The coring styletincludes an elongated body, a tip, a sampling notch in the body adjacentto the tip, and at least one ferrule spaced along the length of thebody. The cannula includes an elongated tubular body that defines alumen sized for sliding passage of the stylet, a cutting edge at theopening of the lumen, and at least one slit along the length of thetubular body. The ferrule has a diameter that permits sliding contactwith the lumen of the cannula and that allows the diameter of theferrule to extend at least partially into the slit. The stylet andcannula are movable relative to each other between a position in whichthe ferrule is disposed within the slit to significantly limit theflexibility of the cannula, and a position where the ferrule is movedout of the slit to allow the cannula to bend or flex as needed. Thecannula may be provided with one or more slit arrays that include slitsat different circumferential locations. The ferrule can then bepositioned in one of the slits in the array to control the direction offlexibility corresponding to the angular orientation of the slit.

BRIEF DESCRIPTIONS OF DRAWINGS

FIG. 1 is a perspective view of the flexible biopsy needle assemblyaccording to the present disclosure.

FIG. 2 is a perspective view of the flexible coring stylet of theassembly shown in FIG. 1.

FIG. 3 is a perspective view of the flexible outer cannula of theflexible coring stylet of the assembly shown in FIG. 1.

FIG. 4 is a sectional view of the flexible outer cannula depicting theorientation of a slit in the cannula shown in FIG. 3.

FIG. 5 is a sectional view of the flexible outer cannula depicting theorientation of another slit in the cannula shown in FIG. 3.

FIG. 6 is a sectional view of the flexible outer cannula depicting theorientation of a further slit in the cannula shown in FIG. 3.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and described in the following written specification. It isunderstood that no limitation to the scope of the invention is therebyintended. It is further understood that the present invention includesany alterations and modifications to the illustrated embodiments andincludes further applications of the principles of the invention aswould normally occur to one skilled in the art to which this inventionpertains.

A flexible biopsy needle assembly 10 is provided as shown in FIG. 1. Theneedle 10 includes a flexible coring stylet 12 that is slidably disposedwithin a flexible outer cannula 14. As shown in FIG. 2, the coringstylet 12 includes an elongated body 20 that may be in the form of aflexible wire. The tip 22 of the stylet 12 may be configured topenetrate tissue, such as a coring tip of known design. A sampling notch24 is provided in the body 20 adjacent the tip 22 and is configured in aconventional manner to accept and trap tissue during operation of thebiopsy needle assembly 10.

Details of the flexible cannula 14 are shown in FIG. 3. The cannulaincludes a tubular body 40 that defines a lumen 42 sized for slidingpassage of the stylet 12 therethrough. The body 40 may define a cuttingedge 43 at the opening of the lumen to sever tissue as the cannula 14 isextended over the sampling notch 24 and tip 22 of the stylet. The styletand cannula may form part of a biopsy apparatus that permitsintroduction of the needle assembly into a target tissue, either withthe stylet retracted or extended relative to the end of the cannula.When tissue prolapses into the sampling notch 24, either the stylet isretracted or, alternatively, the cannula is extended so that the cuttingedge 43 severs the tissue held within the sampling notch. The needleassembly is then withdrawn with the tissue sampling protected within thecannula. The proximal end of the stylet and needle may be configured forengagement within a handpiece configured to permit manipulation andoperation of the stylet and needle to perform a biopsy. The handpiecemay be of a variety of configurations, such as the handpiece disclosedin U.S. Pat. No. 7,048,694, issued on May 23, 2006, to the assignee ofthe present invention, the disclosure of which is incorporated herein byreference.

In many instances it is desirable that the needle assembly exhibit acertain amount of flexibility to navigate to the target tissue site.Thus, the body 20 of the stylet 12 is flexible. The outer cannula 14 islikewise made flexible, in part by the imposition of slits in thetubular body 40 of the cannula. The cannula body also may be formed of amaterial with sufficient flexibility to bend along the length of thecannula and most particularly at the slits formed in the body. Theamount of bending is calibrated by the number and location of the slitsas well as the width of the slits.

The flexible cannula 14 shown in FIG. 3 includes a series of slit arrays44 spaced along the length of the tubular body 40. In the illustratedembodiment, each slit array includes three generally V-shaped slits 45,46 and 47 cut into the tubular body, with the slits spanning about 180°of the circumference of the body. Successive slits are oriented atapproximately 45° intervals. Thus, as shown in the cross-sectional viewsof FIGS. 4-6, the slit 45 is offset about 45° counter-clockwise relativeto the vertical, slit 46 is vertically aligned and slit 47 is offsetabout 45° clockwise from the vertical. As can be seen in FIG. 3, thisarrangement of slits in each slit array 44 produces a repeated patternof slits along the length of the tubular body 40. Slit arrays may extendalong the entire length of the cannula, or may be limited to specificlocations along the length of the body where greater flexibility isdesired.

The elongated or wire body 20 of the stylet 12 is provided with a seriesof ferrules 28 spaced along the length of the body. The ferrules 28 arespaced so that a ferrule may be aligned with each of the slit arrays 44in the outer cannula 14. More specifically, the ferrules may be spacedso that all of the ferrules are simultaneously aligned with one of theslits in each array. In one specific embodiment, the ferrules are spacedso that the distance l₁ between immediately successive ferrules (FIG. 2)corresponds to the distance between slit 45 in one slit array and middleslit 46 in the immediately successive array. Similarly, the distance l₂between every other ferrule corresponds to the distance between slit 45in one slit array and last slit 47 in the next successive array. It canbe noted that the distance l₁ between adjacent successive ferrules 28 isgreater than the distance between the slits 45 and 47 in each slitarray.

With this arrangement of slits and ferrules, it can be seen in FIG. 1that a ferrule is positioned within a slit 46 of the first array 44 aand within slit 45 of the second array 44 b. Since the length l₁ isgreater than the length of a slit array 44, the next ferrule of thestylet 12 is disposed within the slit 47 of the fourth array 44 d, whilethere is no ferrule in the third slit array 44 c.

In one embodiment, each ferrule 28 is provided with a cylindricalcentral portion 29 that is flanked on each side by a conical portion 30.The central portion 29 has a diameter sized to extend at partially intoone of the slits 45, 46, 47. When the central portion 29 of a ferrule 28is disposed within a slit, such as slit 45, any bending of the tubularbody 40 of the cannula is prevented or significantly limited. When theferrule is moved out of a slit and into the portion of the body 40between slits, the bending function of the slit is no longer compromisedand the cannula is free to bend at the slit as desired. The conicalportions 30 facilitate dislodging the cylindrical central portion 29from a slit. The ferrules can be positioned in particular ones of theslits 45, 46, 47 to control the direction of flexibility correspondingto the angular orientation of the particular slit (as depicted in FIGS.4-6).

In another feature, the ferrules 28 may be spaced along the length ofthe body or wire 20 to help stabilize the wire as the stylet 12 istranslated within the lumen 42 of the cannula. In particular, theferrules prevent buckling of the wire 20 as the stylet is extendeddistally from the cannula and into the target tissue. To accomplish thisfeature, the central portion 29 of each ferrule may be sized for a closerunning fit with the lumen 42 of the outer cannula 14.

It should be understood that the components of the biopsy needleassembly 10 disclosed herein are formed of medical grade materials. Thetubular body 40 of the outer cannula 14 and the wire body 20 of thestylet are further formed of a material that is sufficiently offlexibility to bend as desired during use, but that is also sufficientlyrigid to be advanced into body tissue and a solid tissue mass withoutcompromise. The stylet 20 may be molded from a common material, or mayincorporate a material for the tip 22 and notch 24 that is differentfrom the body 20. Similarly, the material of the body 20 may bedifferent from that of the ferrules 28, with the ferrules affixed to thebody in a conventional manner, such as by welding, adhering or shrinkfit.

It is intended that the specification, drawings and examples beconsidered as exemplary only, with the true scope and spirit of theinvention being indicated by the following claims. It should beunderstood that only the preferred embodiments have been shown anddescribed and that all changes and modifications that come within thespirit of the invention are desired to be protected.

1. A flexible biopsy needle assembly, comprising: a flexible coringstylet having an elongated body, a tip, a sampling notch provided in thebody adjacent to the tip, and at least one ferrule spaced along thelength of the body, the ferrule defining a diameter; and a flexibleouter cannula having an elongated tubular body defining a lumen sizedfor sliding passage of the stylet therethrough, a cutting edge at theopening of the lumen, and at least one slit disposed along the length ofthe tubular body, wherein the diameter of the ferrule is sized to extendat least partially into the slit when the ferrule is aligned with saidslit.
 2. The flexible biopsy needle assembly of claim 1 wherein theouter cannula includes a slit array including at least two slits spacedapart along the length of said tubular body.
 3. The flexible biopsyneedle assembly of claim 2 wherein the at least two slits span about 180degrees of the circumference of said tubular body.
 4. The flexiblebiopsy needle assembly of claim 2 wherein the at least two slits areoriented at about 45 degree intervals around the circumference of saidtubular body.
 5. The flexible biopsy needle assembly of claim 4 whereinsaid slit array includes three slits, a first one of said slits offsetabout 45 degrees counter-clockwise from a vertical diameter through saidtubular body, an immediately successive second one of said slits isaligned substantially along said vertical diameter, and an immediatelysuccessive third one of said slits is offset about 45 degrees clockwisefrom said vertical diameter.
 6. The flexible biopsy needle assembly ofclaim 5 wherein: said outer cannula includes at least two of said slitarrays disposed apart along the length of said tubular body; and saidcoring stylet includes at least two ferrules spaced apart along thelength of said body of the stylet so that one each of said ferrules isaligned with one each of said slit arrays.
 7. The flexible biopsy needleassembly of claim 6 wherein said at least two ferrules are spaced sothat each of the ferrules is simultaneously aligned with one of theslits in each slit array.
 8. The flexible biopsy needle assembly ofclaim 7 wherein said at least two ferrules are spaced so that one ofsaid ferrules is aligned with said first one of the slits in each slitarray and a second one of said ferrules is aligned with said second oneof said slits in each slit array.
 9. The flexible biopsy needle assemblyof claim 1 wherein each ferrule includes a cylindrical central portionthat is flanked on each side by a conical portion.
 10. The flexiblebiopsy needle assembly of claim 9 wherein said diameter is defined atsaid central portion.
 11. A flexible biopsy needle assembly, comprising:a flexible coring stylet having an elongated body, a tip, a samplingnotch provided in the body adjacent to the tip, and at least one ferrulespaced along the length of the body; and a flexible outer cannula havingan elongated tubular body defining a lumen sized for sliding passage ofthe stylet disposed within the cannula, a cutting edge at the opening ofthe lumen, and at least one slit array including at least two slitsspaced apart along the length of the tubular body; wherein the styletand cannula are movable between a position in which at least one ferruleis disposed within at least one slit to limit bending of the cannula atsaid at least one slit, and a position in which the ferrule is moved outof the slit to no longer limit bending of the cannula at said at leastone slit.
 12. The flexible biopsy needle assembly, wherein said at leasttwo slits are separated around the circumference of said tubular body sobending is limited in different angular orientations depending uponwhich one of said at least two slits a ferrule is positioned within.